Device and method for recording hand-written information

ABSTRACT

A device for recording hand-written information in the form of characters, symbols, graphs, drawings, calligraphy and similar hand-written information defined by a hand movement, comprises recording means ( 3 ) which are adapted to be moved by a hand which carries out the hand movement and to record a plurality of images with partially overlapping contents while the recording means are being moved. The device further comprises image-processing means ( 4 ) which are adapted to determine the relative position of the images with the aid of the partially overlapping contents for providing a description in digital format of how the unit has been moved and, in this way, a digital representation of the hand-written representation. A method of recording hand-written information is also disclosed.

This application claims the benefit of Provisional Application No.60/091,123, filed Jun. 30, 1998.

FIELD OF THE INVENTION

The present invention relates to a device for recording hand-written inthe form of characters, symbols, graphs, calligraphy and similarhand-written information defined by a hand movement, comprisingrecording means which are adapted to be moved by a hand which carriesout the hand movement and which is adapted to record a plurality ofimages with partially overlapping contents while the recording means arebeing moved. The invention also relates to a method for recordinghand-written information.

BACKGROUND OF THE INVENTION

Today, practically all information processing takes place in computers.The information processed often consists of text which is input to thecomputer by the intermediary of a keyboard. If the text which is to beinput has already been written on a sheet of paper, a scanner issometimes used for the inputting.

Sometimes there is a need for inputting hand-written or otherhand-generated information to a computer. An example of this is when onewishes to input a person's signature. Presently, this can be carried outby scanning the signature or by the person writing his signature withthe aid of a mouse in a drawing program.

Certain smaller computers, so-called pocket computers, have an interfaceenabling inputting of hand-written text with the aid of a pen. Morespecifically, such computers have a touch-sensitive screen, upon whichthe user writes with a pen. The computer records the movement of the penacross the screen. ICR software (ICR=Intelligent Character Recognition)identifies the characters represented by the recorded movement andstores them in character-coded format in the computer. A drawback ofthis technique is that it requires access to a touch-sensitive screen.

Moreover, by way of JP 03265023, it is known to input hand-written textto a computer with the aid of a pen whose tip is provided with a ball.When one “writes” with the pen on a substrate, the ball rolls. With theaid of information about how much and in which direction the ball ismoving, the computer can determine how the pen is being moved. Adrawback of this device and other devices based on moving mechanicalcomponents is that the moving component makes the device more difficultto manufacture and less durable.

Furthermore, EP 0 629 759 discloses a device for storing hand-writtentext in the form of an image. This device has no moving parts. Itcomprises a pen tip and a CCD area sensor which is used to reproducethat written with the pen tip. In one embodiment, the device has the pentip at a first end and the CCD sensor at a second end. In this case, theuser first writes with the pen tip and then turns the device andactivates the CCD sensor to reproduce what has already been written. Inanother embodiment, the pen tip and the CCD sensor are located at thesame end of the device. In this case, the CCD sensor continuouslyreproduces what is being written by recording images. The images whichhave partially overlapping contents are put together to a compositeimage of what has been written. When the written information is to beshown, the composite image is shown.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an alternative methodand an alternative device for recording hand-written information in theform of characters, symbols, graphs, calligraphy and similarhand-written information defined by a hand movement.

This object is achieved by a device according to claim 1 and a methodaccording to claim 18. Preferred embodiments are stated in thesubclaims.

Thus, according to a first aspect, the invention relates to a device forrecording hand-written information in the form of characters, symbols,graphs, drawings, calligraphy and similar hand-written informationdefined by a hand movement. The device comprises recording means adaptedto be moved by a hand which carries out the hand movement and to recorda plurality of images with partially overlapping contents while therecording means are being moved. The device further comprisesimage-processing means which are adapted to determine the relativeposition of the images with the aid of the partially overlappingcontents for providing a description in digital format of how therecording means have been moved and, in this way, a digitalrepresentation of the hand-written information.

Accordingly, the device is based on the idea of using images. However,the images are not used like in prior art to reproduce the hand-writteninformation but are instead used to determine how the recording meansare moved when a user performs the hand movement, e.g. “writes” or“draws” something. The device thus need not store images of thehand-written information but it is sufficient to store information aboutthe movement. This also means that hand-written information can be inputto the computer without any information simultaneously being “written”with ink or some colorant from a pen tip on a writing surface. Theinformation can be written directly in the air if only the recordingmeans are directed at a surface which gives the images contents makingit possible to determine how the images overlap. It goes without sayingthat the device can also be provided with a pen tip, and“colorant-based” writing can occur simultaneously with the electronicrecording. In this case, however, the colorant-based writing need notoccur within the field of vision of the recording means. When thehand-written information is to be shown after recording, this is carriedout on the basis of the stored description of how the recording meanshave been moved.

Thus, the device carries out a digitisation of the hand movement so thata computer can process the information represented by the hand movement.In this context, it should be pointed out that the movement of therecording means is represented by the projection of the end of therecording means upon the surface at which the recording means isdirected.

The image-processing means are preferably implemented with the aid of asuitably programmed processor. It can also be implemented entirely inhardware or in some combination of hardware and software.

In an advantageous embodiment, the device is adapted to store saiddescription in digital format. It may then, for instance, show therecorded hand-written information by means of the description.Alternatively, the description can be forwarded to, for instance, apersonal computer where showing can occur.

A major advantage of the device is that the image recording function canbe used for other purposes as well, thus making it possible to provide adevice with several different fields of application. For example, theimage recording function can be used for inputting text and images whichare already defined on some form of information carrier by imaging thetext and/or the images with the aid of the sensor. This gives the useraccess to a completely new tool enabling him to work more efficiently.With this single tool, the user can thus record text and imageinformation from different sources and supplement it with hand-writteninformation. In this way, the device can become an important tool forstudents, office staff, and other individuals whose work involvesinformation processing.

Suitably, the description comprises a plurality of movement vectors eachindicating how the unit has been moved between the recording of twoimages. The movement vectors can be described with the aid of thecoordinates of a certain point in the first image and the coordinates ofthe same point in the second image expressed in some suitable coordinatesystem. The movement vectors constitute a memory-saving way of storingthe description of how the recording unit has been moved.

In some applications it may be advantageous for the computer to know howthe recording unit has been moved during the hand movement. This may,for example, be the case if one wishes to input calligraphy or otherinformation corresponding to lines which are not of uniform thickness.For this purpose, the description may include turning indications, eachindicating how the recording unit has been turned between the recordingof two images.

Furthermore, in one embodiment, the device is adapted to determine thespeed at which the recording unit has been moved between the recordingof two images. In this embodiment, the device can thus determine thespeed in different parts of the path of movement defined by the handmovement. This may be interesting if, for example, one wishes to checkthe authenticity of a signature, for which purpose the device mayfurther be adapted to compare the speed thus determined withpre-recorded speed data in order to check that the signatory really isthe same person who signed the earlier signature, from which therecorded speed data was obtained.

As mentioned by way of introduction, the information one wishes toprocess in a computer often consists of text, i.e. various types ofcharacters. For this reason, the device is advantageously adapted toidentify the characters with the aid of the description in digitalformat of how the recording unit has been moved and to store them incharacter-coded format. ICR software is advantageously used for thispurpose. An advantage of storing the inputted information incharacter-coded format in the device is that this requires less memoryspace.

Advantageously, the device has a light-sensitive sensor means with atwo-dimensional sensor surface for recording the images. In thiscontext, a two-dimensional sensor surface refers to the fact that thesensor surface must be able to image a surface with a matrix of pixelsso that images with overlapping contents can be recorded. A CCD sensorand a CMOS sensor are examples of suitable sensors.

The determination of the relative position of the images should becarried out both horizontally and vertically in order to enable theinputting of hand-written information defined by arbitrary handmovements.

While the recording unit is being moved, it is directed at a surfacewhich is imaged with the aid of the images. The unit can be passed overthe surface in contact with the same, in which case the hand movement iscarried out in the same way as if one were writing or drawing on thesurface with a pen. As an alternative, it can be held at a distance fromthe surface, which is thus not required to be an even surface but rathercan have any kind of topography, in which case the hand movement iscarried out in the same way as if one were writing or drawing in theair. The purpose in both cases is that the recording unit shallcontinuously record images of what is located within its field of visionalong its path of movement.

In order to make it easier for the user to “see” what he is writing ordrawing by means of the recording unit, the device preferably comprisestracing means for indicating on the surface how the unit is being moved.The tracing means can, of course, comprise a pen function, but,preferably, they should leave no permanent marks on the substrate atwhich they are directed. For example, they can comprise an illuminationmeans adapted to project light upon the surface.

In a preferred embodiment, the recording means and the image-processingmeans are arranged in a common casing, which is adapted to be moved bythe hand making the hand movement. It then becomes a tool which is easyfor the user to carry along and which, consequently, is easy to use inall types of situations. Of course, the recorded, hand-writteninformation is forwarded from the device to, for instance, a stationarycomputer.

In an alternative embodiment, the recording means can be arranged in afirst casing and the image-processing means in a second casing, such asa stationary computer, to which the recording means are connected.

The advantage of the first-mentioned alternative is the fact thatsmaller amounts of data need be transferred from the device to thecomputer.

In addition, in a particularly preferred embodiment, the device isadjustable to an operational mode in which it is adapted to recordpredefined information, especially text, which is located on aninformation carrier by imaging the information with the aid of aplurality of images with partially overlapping contents. In thisembodiment, the capability of the device to record images is utilised intwo ways, something which a user obviously finds attractive since he isnot obliged to use two different tools with different technicalsolutions for these functions.

Moreover, the device is advantageously adjustable to a furtheroperational mode in which it is adapted to image an object located at adistance from the device. In this operational mode, the device thus hasthe function of a camera. This operational mode may require the deviceto be equipped with an adjustable lens system which permits sharpimaging also at longer distances.

In addition, the device can advantageously be provided with atransceiver for wireless communication with an external unit. In thisway, information can be transferred between the device and, for example,an external computer. The transceiver can be an IR transceiver, a mobileradio transceiver, or some other suitable transceiver.

According to a second aspect of the invention, it relates to a methodfor recording hand-written information in the form of characters,symbols, graphs, drawings, calligraphy and similar hand-writteninformation defined by a hand movement, comprising the steps of moving adevice with a hand which carries out the hand movement; recording aplurality of images with overlapping contents while the device is beingmoved; and determining the relative position of the images with the aidof the partially overlapping contents for providing a description indigital format of how the device has been moved and, in this way, adigital representation of the handwritten information. The method hasthe same advantages as those described above with respect to the device.

According to a third aspect of the invention, it relates to a method fordetermining the position of a device which is adapted to record aplurality of images while being moved, the images being recorded withpartially overlapping contents which are used to determine the positionof the device. This aspect of the invention can, for example, be usedfor solving the problems associated with determining the position ofthree-dimensional mice. A three-dimensional mouse is a control devicewith at least six degrees of freedom. Presently, accelerometers are usedfor determining how the three-dimensional mouse is moved. The drawbackof these accelerometers is that they are only capable of determiningrelative positions. Consequently, they are unable to determine when thecontrol device has been moved in such a way that it has returned to itsoriginal position. If, instead, a three-dimensional mouse is equippedwith one or more devices with the above-described structure, each devicecan be used for determining the translational position along and therotational position about an axis by recording images with partiallyoverlapping contents. By comparing each image with the image in theoriginal position, it can be determined when the device returns to theoriginal position. Moreover, by determining the relative position of theimages and with knowledge of the image recording frequency, it ispossible to determine the speed of the movement, the distance and thedirection of the movement, and thus the current position.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of an example showinghow the invention can be implemented, with reference to the accompanyingdrawings, in which

FIG. 1 schematically shows an embodiment of a device according to theinvention;

FIG. 2 is a block diagram of the electronic circuitry in an embodimentof a device according to the invention;

FIG. 3 is a flowchart showing the functioning of the device;

FIG. 4 is a schematic illustration showing how a surface is imaged inconnection with the inputting of hand-written information;

FIG. 5 illustrates how the inputted information can be shown on adisplay;

FIG. 6 is a flowchart illustrating how the device is used in a scannermode; and

FIGS. 7 a–7 e schematically show how text is recorded in the scannermode.

DESCRIPTION OF A PREFERRED EMBODIMENT

In the embodiment of the device according to the invention shown in FIG.1, it comprises a casing 1 having approximately the same shape as aconventional highlighter pen. One short side of the casing has a window2, which is intended to abut against or be held at a distance from asurface when information is to be input to a computer with the aid ofthe device. The window 2 is somewhat recessed in the casing in order notto wear against the paper.

The casing 1 essentially contains an optics part 3, an electroniccircuitry part 4, into which information is fed, and a power supply 5.

The optics part 3 is used for a recording images and thus is an exampleof how the recording means can be implemented. It comprises alight-emitting diode (LED) 6, a lens system 7, and a light-sensitivesensor 8, which constitutes the interface with the electronic circuitrypart 4.

The task of the LED 6 is to illuminate a surface which is currentlylocated under the window. A diffuser 9 is mounted in front of the LED 6for diffusing the light.

The lens system 7 has the task of projecting an image of the surfacelocated under the window 2 on the light-sensitive sensor 8 as accuratelyas possible. If the sensor 8 has a smaller light-sensitive area than thewindow 2, the lens system 7 is also required to reduce the image.

In this example, the light-sensitive sensor 8 comprises atwo-dimensional, square CCD unit (CCD=charge coupled device) with abuilt-in A/D converter. Such sensors are commercially available. Thesensor 8 is mounted at a small angle to the window 2 and on its ownprinted circuit board 11.

The power supply to the device is obtained from a battery 12, which ismounted in a separate compartment 13 in the casing.

The block diagram in FIG. 2 schematically shows the electronic circuitrypart 4. This is used, among other things, for processing the recordedimages and thus is an example of how the image-processing means can beimplemented. It comprises a processor 20, which by the intermediary of abus 21 is connected to a ROM 22, in which the programs of the processorare stored, to a read/write memory 23, which constitutes the workingmemory of the processor and in which the images from the sensor as wellas identified and interpreted characters are stored, to a control logicunit 24, as well as to the sensor 8 and the LED 6. The control logicunit 24 is in turn connected to a number of peripheral units, comprisinga display 25, which is mounted in the casing, an IR transceiver 26 fortransferring information to/from an external computer, buttons 27, bymeans of which the user can control the device and specifically adjustthe device between a first mode in which hand-written information is tobe input, a second mode in which the device operates as a scanner, and athird mode in which the device operates as a camera, a tracer LED 28which emits a light beam, making it easier for the user to know whichinformation he is inputting, as well as an indicating device 29, e.g. anLED, indicating when the pen is ready to record information. Controlsignals to the memories, the sensor, and the peripheral units aregenerated in the control logic unit 24. The control logic also handlesgeneration and prioritisation of interrupts to the processor. Thebuttons 27, the IR transceiver 26, the display 25 and the tracer LED 28,and the LED 6 are accessed by the processor writing and reading in aregister in the control logic unit. The buttons 27 generate interruptsto the processor 20 when they are activated.

The operation of the device will now be described, presupposing that theuser first wishes to input handwritten text. The user directs the deviceat a surface having some kind of pattern. For example, the surface canbe a sheet of paper with text on it, a wall, or a bowl of sweets. Hepresses a button 27 to activate the device and subsequently “writes” thetext he wishes to input with the device directed at the selectedsurface. The tracer LED 28 successively indicates the path of movementon the surface by means of a luminous spot to give the user an idea ofthe movement. When the user activates the pen, the processor 20 commandsthe LED 6 to begin generating strobe pulses at a predeterminedfrequency, suitably about 25 Hz, whereupon the images recorded by thesensor are stored in the read/write memory 23. When the user has writtenthe information he wishes to input, he releases the button 27, whereuponthe processor 20 turns off the LED 6. The user can then control thedevice to show the inputted information on the display 25 or to transferit to an external computer by the intermediary of the IR transceiver 26.The possibility of showing the scanned information directly on thedisplay has proven very important since a user often wishes to verifythat the correct information has been scanned.

The flowchart in FIG. 3 shows in more detail how the device functions inconnection with the inputting of hand-written information. In step 301,images with overlapping contents are scanned while the device is beingmoved relative to the surface at which it is directed. The scannedimages are stored in the read/write memory 23. The images are stored asimages, i.e. with the aid of a plurality of pixels, each having a greyscale value in a range from white to black.

As soon as an image has been recorded, the process begins of determininghow the current image and the previous image overlap, step 302, i.e. inwhich relative position the best match is obtained between the contentsof the images. For this purpose, every possible overlap position betweenthe images is examined, at the pixel level, and an overlap measurementis determined as follows:

1) For each overlapping pixel position, the grey scale values of the tworelevant pixels are added up if the latter are not white. Such a pixelposition in which none of the pixels are white is designated a plusposition.

2) The grey scale sums for all the plus positions are added up.

3) The neighbours of each pixel position are examined. If an overlappingpixel position is not a neighbour of a plus position and consists of apixel which is white and a pixel position which is not white, the greyscale value of the non-white pixel is subtracted, possibly multiplied bya constant, from the sum in point 2).

4) The overlap position providing the highest overlap measurement asstated above is selected. In the resulting composite image the meanvalue of the grey scale value of the overlapping pixels is used. In thisway, noise can be suppressed in the overlap area. The putting-togetheris thus carried out both vertically and horizontally. If it is detectedthat, when being put together, the images do not end up on a horizontalline, the composite image is suitably adjusted so that it becomeshorizontal, for example by turning the composite image.

Our Swedish Patent Application No. 9704924-1 and the corresponding U.S.Pat. No. 6,563,951, describe an alternative way of matching the imagesin order to find the best overlap position. The content of theseapplications is herewith incorporated by reference.

When the relative position of the two images has been determined, theprocessor 20 determines a movement vector, in step 303, which indicateshow far and in which direction the device has been moved between therecording of the images. The movement vector is stored in the memory aspart of a digital description of how the device has been moved. Theprocessor also determines how the second image is turned in relation tothe first one, i.e. how the device has been turned between the recordingof the images. This is carried out by examining the overlap in differentturning positions between the first and the second image. The turning isstored as a turning indication in the memory and it, too, constitutes apart of the description of how the device has been moved. When this stephas been completed, the first image is discarded and the second imagebecomes the first image, after which the putting-together of thesubsequent scanned image with this new first image is commenced. Itshould be pointed out that in most cases, movement vectors and turningindications need not be determined in a separate step but they can beobtained as a direct result of the determination of the relativeposition of the images. As is evident from that described above, steps301–303 can proceed more or less in parallel.

When the device detects that the inputting of an information unit iscomplete, for instance by the user releasing the button 27 or by thedevice not being moved for at least a predetermined period of time, thedevice decides whether or not the inputted information is to beinterpreted, step 304. If the user has indicated by pressing a buttonthat the inputted information is text information which is to beinterpreted, the processor 20 reads in the movement vectors in thedescription of the information unit in question to an ICR module whichidentifies which character the movement vectors represent. Subsequently,the identified character is stored in character-coded format in thememory. The interpreted character can be shown on the display 25 if theuser indicates this preference by pressing a button. If the user has notindicated that the information is to be interpreted, no further actionis taken with respect to the information unit and the device is ready torecord further information units.

FIG. 4 schematically shows how images with overlapping contents arerecorded when a device as described above is directed at a sheet ofpaper and the device is moved in a path of movement forming the letter“R”. For the sake of simplicity, the contents of the images are notshown in FIG. 4.

FIG. 5 shows how an inputted letter R can be reproduced on the displayof the device on the basis of the relative positions determined by thedevice for the images in FIG. 4. Thus, in this case, the device shows an“image” of the inputted character with the aid of the movement vectors,not an interpreted character.

The above description outlines how the device can be used in a firstmode for inputting hand-generated information. However, in a secondmode, the device can also be used as a scanner, i.e. for scanningpredefined text and image information on an information carrier. If theuser wishes to use the device in this way, he indicates this by pressinga button in a suitable manner.

Suppose now that the user wishes to scan text from a sheet of paper. Inthis case, the user directs the device at the sheet of paper with thetext at the location where he wishes to begin recording a charactersequence. He presses the button 27 to activate the pen and passes itover the text which is to be recorded, following the text in the samemanner as when one reads the text. The tracer LED 28 emits a light beamwhich makes it easier to follow the lines. When the user activates thepen, the processor 20 controls the LED 6 to scan images in the same wayas described above with respect to inputting of hand-generatedinformation. When the user has passed the device over the selected textor has come to the end of a character line, he lifts the pen off thesheet of paper and releases the activating button, whereupon theprocessor 20 turns off the LED 6.

The flowchart in FIG. 6 illustrates in more detail how the deviceoperates in this mode. In step 601, the images with overlapping contentsare scanned and stored in the same way as in the first mode.

In step 602, the best overlap position is determined for each pair ofimages in the same way as described above for the first mode. In thisposition, the images are put together into a composite image comprisinga plurality of characters, possibly a whole line.

In step 603, the software of the processor 20 divides the compositeimage into sub-images, each comprising only one character. The purposeof this is to create input signals to the OCR software which is tointerpret the characters. The division is effected by adding up the greyscale values of the pixels for each pixel row and each pixel column inthe composite image. By studying the local intensity minima for the rowsums and column sums thus obtained, boundaries can be determined for theextent of each character in the image.

In step 604, each of the sub-images is scaled down to a predeterminedpixel format by dividing the sub-image into groups of pixels, each ofwhich is replaced by a pixel whose grey scale value corresponds to themean value of the grey scale values of the pixels included in the group.If necessary, a like downscaling can be carried out between other stepsof the method according to the invention. Further, the character iscentred with respect to its point of balance and the grey scale valuesare normalised so that the sum of the square of the grey scale value ofeach pixel is given a fixed value.

Subsequently, in step 605, each character in the composite image of thecharacter sequence recorded is interpreted. The grey scale values of thepixels which together constitute a sub-image containing only onecharacter are fed as input signals to an OCR software. In step 606, theidentified character is stored using a predetermined character codeformat, for example ASCII code, in the read/write memory 23 in a memoryarea for interpreted characters. When the character identification andstoring in character-coded format is completed, the processor activatesthe indicating device 29 to inform the user that it is ready to record anew character sequence, step 607. Subsequently, it goes back to step601.

The above steps in both the first and the second mode are thus carriedout by the processor 20 with the aid of the associated units andsuitable software. Such software can be created by the skilled personwith the aid of the above instructions if it is not commerciallyavailable.

FIGS. 7 a–7 e illustrate how the character sequence “Flygandebäckasiner” is scanned. FIG. 7 a shows the text on a sheet of paper,which also has a certain amount of “dot noise” in the form of smallblack spots. FIG. 7 b shows the images which are being recorded with theaid of the sensor. As can be seen from this figure, the contents of theimages partially overlap. For example, the letter l appears completelyin image No. 1 and partially in image No. 2. The degree of overlappingdepends on the traction speed, i.e. the speed with which the user pullsthe device over the text in relation to the frequency with which thecontents of the sensor are read out. FIG. 7 c shows what the wholecomposite image looks like. It should be noted that the image is stillstored in the form of pixels. FIG. 7 d illustrates the division of thecomposite image into sub-images. FIG. 7 e shows the scaled andnormalised letters which are used as input signals to the neuralnetwork. When the method has been carried out; the text “Flygandebäckasiner” is stored in the read/write memory of the device as ASCIIcode.

As stated above, the device can also be used in a third mode, the cameramode, for recording images of objects which are located at a distancefrom the device. In order to effect sharp imaging at various distances,the lens system 7 can be adjustable between two fixed positions, onebeing used in the scanner mode and the other in the camera mode.Alternatively, the position of the lens system 7 can be slidablyadjustable for providing an autofocus function. The adjustment of thelens system can be effected by means of the same technique as is used incameras.

1. A method of recording handwritten information defined by a handmovement, said method comprising: providing a surface having apreexisting pattern; providing an imaging device; moving the imagingdevice with a hand which is carrying out the hand movement relative tothe surface while recording with the imaging device a plurality ofimages of the preexisting pattern with partially overlapping contents;comparing said images in pairs to determine, with the aid of thepartially overlapping contents, a relative shift of the preexistingpattern between each pair of images; and providing a description indigital format of how the imaging device has been moved over the surfacebased at least in part on the thus-determined relative shifts.
 2. Amethod according to claim 1, wherein the handwritten informationcomprises characters and further comprising identifying the characterswith the aid of the description and storing them in character-codeddigital format.
 3. A method according to claim 1, further comprisingdisplaying the handwritten information based on said description.
 4. Amethod according to claim 1, further comprising determining, on thebasis of the partially overlapping contents of the images, the speed atwhich the device has been moved between recording of two images.
 5. Amethod according to claim 4, further comprising comparing the speed withpre-recorded speed data for checking the authenticity of the handwritteninformation.
 6. A method according to claim 1, further comprisingindicating on the surface the movement of the device.
 7. A methodaccording to claim 1, further comprising recording pre-existinginformation on an information carrier by imaging the pre-existinginformation with the aid of a plurality of images with partiallyoverlapping contents.
 8. A method according to claim 7, furthercomprising adjusting the device from a first operational mode forrecording the handwritten information to a second operational mode forrecording the pre-existing information.
 9. The method according to claim1, further comprising storing the handwritten information by storingsaid description.
 10. The method according to claim 1, wherein saidcomparing the images in pairs is performed in parallel with saidproviding a description in digital format.
 11. A method according toclaim 1, wherein the imaging device comprises a light-sensitive sensorwith a two-dimensional sensor surface for recording the images, and alight source, further comprising selectively activating the light sourceto illuminate said surface while controlling said light-sensitive sensorto capture images of the thus-illuminated surface.
 12. A methodaccording to claim 11, further comprising selectively activating thelight source to strobe at a predetermined frequency.
 13. A methodaccording to claim 1, further comprising selectively operating atransceiver to transfer said description to an external device.
 14. Amethod according to claim 13, wherein the transceiver communicateswirelessly with the external device.
 15. A method according to claim 1,further comprising operating a pen tip connected to the imaging deviceto generate permanent marks on said surface, said marks beingundetectable to said imaging device.
 16. A method according to claim 1,further comprising operating a pen tip connected to the imaging deviceto generate permanent marks on said surface, such that said marks areexcluded from said images.
 17. A method according to claim 1, whereinsaid preexisting pattern includes graphics printed on the surface.
 18. Amethod according to claim 1, wherein said comparing said images in pairscomprises evaluating every possible candidate shift between said pair ofimages.
 19. A method according to claim 1, wherein said comparing saidimages in pairs comprises evaluating, based on a plurality of elementvalues for each image, different candidate shifts between said pair ofimages by: applying said candidate shifts to one image with respect tothe other image in said pair of images; effecting, for each candidateshift, a comparison of each element value of said one image and anoverlapping element value of said other image; and when the comparisonfulfills a predetermined criterion, selectively updating a match ratevalue for the candidate shift.
 20. A method according to claim 19,wherein said comparing said images in pairs further comprisesdetermining said relative shift as the candidate shift that has anoptimum match rate value.
 21. A device for recording handwritteninformation defined by a hand movement, comprising: an imaging deviceconfigured to be moved by a hand which carries out the hand movement andto record a plurality of images with partially overlapping contents of asurface having a preexisting pattern while the imaging device is beingmoved; and an image processor configured to compare said images in pairsto determine, with the aid of the partially overlapping contents, arelative shift of the preexisting pattern between each pair of imagesand to provide a description in digital format of how the imaging devicehas been moved over the surface based at least partially on thethus-determined relative shifts.
 22. A device according to claim 21,wherein said description comprises a plurality of movement vectors eachindicating how the imaging device has been moved between said pair ofimages.
 23. A device according to claim 21, wherein said descriptioncomprises turning indications, each indicating how the imaging devicehas been turned between said pair of images.
 24. A device according toclaim 21, wherein said device is configured to determine, on the basisof the partially overlapping contents of the images, the speed at whichthe imaging device has been moved between said pair of images.
 25. Adevice according to claim 24, wherein said device is configured tocompare the speed with pre-recorded speed data for checking theauthenticity of the inputted information.
 26. A device according toclaim 21, wherein the handwritten information comprises characters andwherein the image processor is further configured to identify thecharacters with the aid of said description and to store the identifiedcharacters in character-coded format.
 27. A device according to claim21, wherein said image processor is configured to determine the relativeshift both horizontally and vertically.
 28. A device according to claim21, further comprising a tracer for indicating on the surface themovement of the imaging device.
 29. A device according to claim 28,wherein the tracer comprises an illuminator which projects light ontothe surface.
 30. A device according to claim 21, wherein the imagingdevice and the image processor are arranged in a common casing which isconfigured to be moved by the hand carrying out the hand movement.
 31. Adevice according to claim 21, wherein the imaging device is arranged ina first casing and the image processor in a second casing.
 32. A deviceaccording to claim 21, wherein said device is adjustable to anoperational mode in which it is configured to record predefinedinformation located on an information carrier, by imaging the predefinedinformation with the aid of a plurality of images with partiallyoverlapping contents.
 33. A device according to claim 21, wherein saiddevice is adjustable to an operational mode in which it is configured toimage an object located at a distance from the device.
 34. A deviceaccording to claim 21, further comprising a display for reproducing thehandwritten information based on said description.
 35. A deviceaccording to claim 21, wherein the imaging device comprises acontroller, a light-sensitive sensor with a two-dimensional sensorsurface for recording the images, and a light source, said controllerselectively activating the light source to illuminate said surface whilesaid light-sensitive sensor is being controlled to capture images of thethus-illuminated surface.
 36. A device according to claim 35, whereinsaid controller selectively activates the light source to strobe at apredetermined frequency.
 37. A device according to claim 21, wherein theimage processor is configured to store said description in a memory. 38.A device according to claim 37, which is configured to selectivelyderive said description from the memory and operate a transceiver totransfer said description to an external device.
 39. A device accordingto claim 38, wherein the transceiver is configured for wirelesscommunication with the external device.
 40. A device according to claim21, further comprising a pen tip for generating permanent marks on saidsurface, said marks being undetectable to said imaging device.
 41. Adevice according to claim 21, further comprising a pen tip forgenerating permanent marks on said surface, said device being configuredto exclude said marks from said images.
 42. A device according to claim21, wherein said preexisting pattern includes graphics printed on thesurface.
 43. A device according to claim 21, wherein the imaging devicecomprises a lens system with automatic focus control.
 44. A deviceaccording to claim 21, wherein the image processor is configured toevaluate every possible candidate shift between said pair of images. 45.A device according to claim 21, wherein the image processor isconfigured to evaluate, based on a plurality of element values for eachimage, different candidate shifts between said pair of images by:applying said candidate shifts to one image with respect to the otherimage in said pair of images; effecting, for each candidate shift, acomparison of each element value of said one image and an overlappingelement value of said other image; and when the comparison fulfills apredetermined criterion, selectively updating a match rate value for thecandidate shift.
 46. A device according to claim 45, wherein the imageprocessor is configured to determine said relative shift as thecandidate shift that has an optimum match rate value.